Like a giant "Lego" set in space, the Station
has many nicknames. For those on the outside, it's easy to just
see it as a large orbiting research center. But for the teams
hard at work helping to assemble it, it's more about the nuts
and bolts. For Sylvie Beland, Flight and Launch Systems Manager
for the Canada Space Agency
(CSA), it's literally about the bolts.
A mechanical engineer, Beland's job is to make
sure all Canadian hardware, including the famous "Canada Arm"
designed for space station, and flight support equipment arrives
at the station safely and in one piece.
Once aboard, all components must be able to handle thermal changes
and be successfully installed, integrated and utilized by the
astronauts. "What astonished me was how much testing, integration,
and verification is necessary for whatever you design," said Beland.
Bolts Were Made for Working
Canada's high-tech robotic arm is something you just want to see
in action. To fit it in the space shuttle,
the 55-foot-long arm is folded in four and placed on a space lab
pallet that fits in the cargo bay. It's attached with eight 40"
bolts so it stays in place during launch. "But because the tension
load in this bolt is very high, it has
to be distributed to smaller bolts via a patented multi-nut mechanism,
so that the torque required by the astronauts to undo the bolts
does not exceed the 25 foot pounds requirement" said Beland. To
deploy the arm, the astronauts have to undo a total of 32 bolts--sequentially,
one turn at a time, approximately 6 turns per bolt--a tough and
The torque required to remove the bolts cannot
exceed 25 foot pounds. The bolts passed thorough testing to ensure
this, but just a little too close for comfort. "So together, as
scientists, we decided to do a more extensive human thermal vacuum
test." This is a big vacuum chamber where astronauts, in spacesuits,
practice with the tools they'll use in orbit. In this vacuum environment
(like space), there is no air, and if for some reason, lubricant
is damaged or absent on some areas, just metal to metal contact--which
increases the friction between the two parts and could lead, under
high loading conditions, to cold welding--so astronauts may require
more torque than necessary. After some modifications, the bolts
All systems go? Not yet. Once removed, these same bolts are stored
in tubes on top of which a slider bar is installed to make sure
they don't float in orbit. But, with the bolt redesign, the slider
bar didn't fit, requiring another fix and more integration testing.
Happy ending--the arm is going up, bolts and all, in April 2001